2015 fantasy novella in the World of the Five Gods (formerly known as
Chalion). Lord Penric, an impoverished nobleman, is on his way to his
betrothal when he comes upon a riding accident. Before he knows what's
happened, he's inherited a demon, and everyone's looking at him as
though he might explode at any moment.

We've learned in earlier novels set in this world that demons are
sentient spirits, able to share a body until that body's death and
grant sorcerous powers to the body's owner; but unless the owner has
hugely strong will, the demon will take over, and that's bad news for
everyone. It transpires that this is not the whole story.

Much of this is because Penric is rather an unusual person: third son
of a minor lordling, who might have liked to be a scholar if the
family could have afforded it, he essentially lacks ambition or
ill-will. His reaction to gaining a demon with Awesome Powers is not
to go burning things down for revenge, but to talk to it. After all,
demons have copies of the memories of their previous hosts…

In fact if other people had kept the promises they made to Penric
everything would have gone much less messily. But they don't, of
course. Power like this isn't easily found.

There are long passages of detailed world-building which lead me to
think that Bujold has heard the tale of the overstuffed armchair;
there's a Free City that's in mild conflict with the old local lords,
lots of detail of what you can get in a market and the sort of food
people eat, and so on. It's something of an observational lesson in
fantasy world construction.

The only real problem is that this novella feels like the beginning of
the real story: it resolves the basic question of broadly how Pen
and the demon are going to go about their lives together, but it's
very much a starting point; it could easily have been the first third
or quarter of a novel, and I'd have liked to read more.

This work is only legally available in a DRM-bound format so I cannot
recommend buying it, but if you don't have my moral objections to
paying for such things you should know that it's very good.